This Could Be A Problem For Facebook

Facebook investors might be wondering just that. Shares of the social giant made a new all-time high and have doubled in just the past three months. The company now sports a staggering $120 billion market cap.

But because of that performance, or perhaps in spite of it, Wall Street has started to warm to the name.

Canaccord Genuity just slapped a "Buy" rating on the stock with $60 price target. For those bad at math, that's a 20% higher from here. This follows Citigroup's Mark May who upgraded Facebook yesterday, saying the company's growth was "sustainable."

But perhaps investors should ask if Wall Street's constant chorus of newfound love for Facebook is sustainable.

With those two upgrades, there are now 37 "buy" ratings, nine "hold" ratings and zero "sell" ratings.

That's right. Of the 46 firms that cover the name, not a single one of them is outright bearish. And that has some investors pretty bearish as now there is no one left to like the stock.

"Don't be afraid to take profits," said Brian Kelly of Brian Kelly Capital. "The analyst upgrades are based on information that is already known and priced-in."

The improvement in Facebook's mobile advertising has driven investor enthusiasm for the name. But some market participants fear that success might set the company up for unrealistic expectations in the future. If mobile can't continue to grow at its torrid pace, the stock could see lots of trouble.

"Last year was a great time to buy the stock," said Enis Tanner ofRiskreversal.com. "Today might be a great time to sell it."